In just five years, approximately one-sixth of the world's population will subscribe to mobile-broadband services, according to a ABI Research report released Tuesday. The research firm projects that Internet-surfing smartphone owners, which make up the majority of mobile-broadband subscribers today, will be joined by iPad and laptop owners who want portable broadband Internet service for their devices. All together, ABI expects they will boost mobile-broadband subscriptions to 1.5 billion in 2015.

It helps that a broadening range of devices can be used as cellular modems, including PC cards, USB modems, internal mini-cards and mobile-hotspot routers, ABI Research said in its report. The forecast also reflects the growing sales of smartphones such as Apple's (AAPL) iPhones and Research In Motion's (RIMM) BlackBerry handheld devices. Almost two-thirds of those smartphones will be equipped with mobile Internet browsers within the next five years, ABI projected in a separate report last month.

If ABI's expectations of growth are correct, you can also expect to see more advertising move to the mobile medium. In another report released last week, ABI forecast that firms will spend about $1.8 billion on location-based advertising using GPS, WiFi and Cell-ID technology in 2015.